diff -r 0042b30216fc lib/galaxy/tools/parameters/basic.py
--- a/lib/galaxy/tools/parameters/basic.py	Tue Nov 06 11:14:22 2012 -0800
+++ b/lib/galaxy/tools/parameters/basic.py	Mon Dec 10 11:26:41 2012 -0600
@@ -715,6 +715,12 @@
             if value not in legal_values:
                 raise ValueError( "An invalid option was selected, please verify" )
             return value    
+    def to_html_value( self, value, app ):
+        if isinstance( value, list ):
+            return value
+        else:
+            return str( value )
+
     def to_param_dict_string( self, value, other_values={} ):
         if value is None:
             return "None"